Compounds of Formula I are disclosed as antihypertensive agents in U.S. Pat. No. 4,296,110, issued Oct. 20, 1981, to A. L. Johnson. ##STR3## where R and R.sub.3 are independently OH, C.sub.1 -C.sub.4 alkoxy or C.sub.6 H.sub.5 CH.sub.2 O;
R.sub.1 is H, CH.sub.3, C.sub.2 H.sub.5, CF.sub.3, isobutyl, isoamyl, --(CH.sub.2).sub.n NHR.sub.5 or ##STR4## R.sub.2 is H or CH.sub.3 ; R.sub.4 is C.sub.1 -C.sub.10 alkyl; --(CH.sub.2).sub.q C.sub.6 H.sub.5 or --(CH.sub.2).sub.r NH.sub.2 ; PA1 R.sub.5 is H or C.sub.1 -C.sub.4 alkyl; PA1 m is 2, 3 or 4; PA1 n is an integer from 1-6; PA1 p is an integer from 1-6; PA1 q is an integer from 0-6; and PA1 r is an integer from 1-6; PA1 R.sub.1 ' is H, CH.sub.3, C.sub.2 H.sub.5, CF.sub.3, isobutyl, isoamyl, (CH.sub.2).sub.n NR.sub.5 COOCH.sub.2 C.sub.6 H.sub.5 or (CH.sub.2).sub.p NH--C(.dbd.NH)NHNO.sub.2 ; PA1 R.sub.2 ' is CH.sub.3, carbobenzyloxy or tert-butoxycarbonyl; PA1 R.sub.3 ' is C.sub.1 -C.sub.4 alkoxy or benzyloxy; PA1 R.sub.4 ' is C.sub.1 -C.sub.10 alkyl, --(CH.sub.2).sub.q C.sub.6 H.sub.5, --(CH.sub.2).sub.r NH-- or COOCH.sub.2 C.sub.6 H.sub.5 ; and PA1 R.sub.5, m, n, p, q and r are as previously defined. PA1 R.sub.3 ' is OX.sup.3, C.sub.1 -C.sub.4 alkoxy or benzyloxy; PA1 R.sub.4 ' is C.sub.1 -C.sub.10 alkyl, --(CH.sub.2).sub.q C.sub.6 H.sub.5 or --(CH.sub.2).sub.r NH--X.sup.4 ; PA1 R.sub.5 is H or C.sub.1 -C.sub.4 alkyl; PA1 m is 2, 3 or 4; PA1 n is an integer from 1-6; PA1 p is an integer from 1-6; PA1 q is an integer from 0-6; PA1 r is an integer from 1-6; PA1 X, X.sup.1, X.sup.2, X.sup.3 and X.sup.4 are protective groups; and PA1 Y is a carboxyl-activating group;
and pharmaceutically acceptable salts thereof.
The same patent also discloses a method of preparing compounds of Formula I by coupling the alkali metal salt of an ester of the formula ##STR5## where R' is C.sub.1 -C.sub.4 alkoxy or benzyloxy, with a suitable derivative of the formula ##STR6## in which Y is ethoxycarbonyloxy, methoxycarbonyloxy, N-oxysuccinimidyl or 4-nitrophenoxy;
The standard protective groups are removed to yield the compounds of Formula I.